1. Field of the Invention
This disclosure relates generally to protection systems for mitigation of damage caused by slug flow and more particularly, to a method and apparatus for protecting against slug flow.
2. Description of the Related Art
In multi-phase flow systems used in the oil and gas industry, crude oil, water and gas are transported from a well through a pipeline system to a process facility. In offshore oil production, the crude oil, water, and gas are generally simultaneously transported through a sub-sea pipeline to gas/liquid separating equipment, such as a separator, which is located on an offshore platform or onshore. This type of multiphase fluid flow results in different types of flow regimes occurring, including slug flow.
Slug flow can be problematic because it consists of alternating liquid and gas surges, which results in an unwanted flow pattern of alternating lack of flow or production starvation, large liquid slugs, and strong gas surges. Alternating patterns of liquid slugs and gas surges being supplied to a separator reduces its efficiency, since the separator is operated with acceptable pressure fluctuations and delivers a lower liquid content in the gas outlet and a lower gas content in the liquid outlet in order to accommodate for the pressure fluctuations.
The liquid slugs can also grow under certain flow conditions, which leads to severe slugging with the above-described unwanted flow patterns and inefficiency. Liquid slugs can also be generated by operational changes, such as with the increase of the fluid production during the start-up of a pipeline.
Monitoring for slug flow can be difficult due to the number of variables involved in the slug flow formation. Measurement of the flow rate in the sub-sea pipeline is difficult due to the multiphase flow therein and can require costly equipment to do so.
Accordingly, there is a need for mitigation of slug flow, which maintains the efficiency of the separator, while maintaining the efficiency of the oil and gas production system. There is a further need for a slug protection and mitigation system that is easily and cost effectively incorporated into the oil and gas production system, while reliably mitigating against damage caused by slug flow. The method and apparatus of the present invention provides for slug flow mitigation and protection.